If you spend the money for Brembo, 18in wheel standard M3, then use the 356mm slotted rotors, to fit and save money. If you have the M3 competition package then you can fit the BBK 380mm slotted. Monster brakes for hard Time Attack racing. Drilled rotors are for the cool look, but are useless on the track.
I burned up my stock pads and rotors, boiled the fluid in one 15 minute race. Cost almost $3k to fix. I found from other racers.
If you really want to save money. Install Castrol SRF brake fluid and a set of HT10, HP Plus or DTC 70 for super aggressive braking with your stock rotors and calipers. Cheap way at only $400.00 to upgrade your brakes. I have raced NASA TT3 with this upgrade all season, no complaints here. Still saving for the BBK kit or the AP Racing kit.